Navies of the world

by Edward W. Very

Woolwich Groove.

Plain Groove.

Various systems of grooves will be found in these guns, corresponding to different stages of development. In the 7-pdr. the French groove is used, having sharp angles, the loading side being at a sharper pitch than the driving. In the 9-pdrs. appears the modified French groove, in which the angles are rounded off and the loading side is at right angles to the driving side. In the 64-pdr. converted gun the plain groove is used. This groove is almost rectangular, the driving side being canted but little. In the 64-pdr. of 64 cwt. the shunt groove is used. This is a double groove, one half being deeper than the other, the rear end of the groove having a shunt by which the studs are turned into the shallow half. The 7-inch muzzle-loaders have the Woolwich groove with a uniform twist. This groove is the final modification of the original French groove. The higher calibres up to the 16-inch gun have the Woolwich groove with an increasing twist. The 16-inch calibre will have the plain multigroove, or the groove ordinarily used for expanding projectiles. The breech-loaders have the Armstrong multigroove, a groove which in section is not unlike a saw-tooth.

7-pdr. Steel R. M. L. 200 lbs.

Introduced into service in 1873. Made of a single block of steel, having no swell at the muzzle, but a small dispart patch into which the fore sight screws. Copper vent bouch. The sight is a plain, centre hind sight set at a permanent angle of deflection of 3°. It seats in a hole bored in the metal of the gun, having a simple clamp-screw to hold it in position. Two sight-bars are used with the gun, one graduated to 6° and the other to 12°, the graduations on both being for intervals of 3´. This gun may be distinguished from the 9-pdr. by the slope at the junction of the reinforce and chase, which is gradual.

9-pdr. Wrought Iron R. M. L. 6 and 8 cwt.

Introduced into service in 1871 and 1873. It consists of two parts—a toughened steel tube, and a jacket composed of two single coils and a trunnion-ring welded together. The cascabel is cut out of the solid end of the steel tube, and is recessed to receive the head of the elevating screw, which is fastened to it by a bolt and keep-pin. The 6 cwt. and 8 cwt. guns differ only in length and weight, the latter being 10½ inches longer. The 7-pdr. and the 9-pdr. are of the same calibre, but the same projectiles cannot be used in both, as the twist is different and the studs on the 7-pdr. projectile are much wider than those of the 9-pdr. The arrangement of the sights is the same for both guns. It is easily distinguished by the abrupt step at the forward end of the jacket.

9-pdr.